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Impact unclear A decrease in the number of deaths from breast cancer cannot be attributed to screening programs, say the authors of a new multinational study.

The research, led by Dr Philippe Autier of the International Prevention Research Institute in France, sought to determine whether the decrease in mortality due to breast cancer was because of earlier detection or better management.

Autier and colleagues in the United Kingdom and Norway compared trends in breast cancer mortality within three pairs of European countries.

The paired countries had similar healthcare services and level of risk factors for breast cancer mortality, but had a gap of 10 to 15 years in implementation of organised mammography screening.

The researchers looked at mortality rates, as well as data relating to mammography screening, cancer treatment, and risk factors for breast cancer death.

They expected to find a reduction in breast cancer mortality appearing sooner in countries with earlier implementation of breast cancer screening programs. But this was not the case.

For example, between 1989 and 2006 deaths from breast cancer fell by 29 per cent in Northern Ireland compared with 26 per cent in the Republic of Ireland despite their screening program beginning 10 years later. Similar results were obtained when the researchers compared data from the Netherlands, Brussels-Wallonia and Flanders, as well as between Sweden and Norway.

The greatest reductions in breast cancer mortality rates were in women aged 40 to 49 years, regardless of the availability of screening in this age group.

Writing in the British Medical Journal, Autier and colleagues suggest that screening has not played a direct part in reducing breast cancer mortality.

"Improvements in treatment and in the efficiency of healthcare systems may be more plausible explanations," the authors write.

One of many factors

Professor Sanchia Aranda, Deputy CEO of Cancer Institute NSW, says the results of the study are consistent with their thinking that "screening is only one element of a complex system to support early detection of cancer."

She says this includes a high level of breast cancer awareness among women and that screening services via primary healthcare providers would have been available prior to implementation of organised screening programs.

Aranda also says that there are many other important outcomes aside from mortality where screening has an important role.

"What we are finding is that screening programs enable you to detect cancers at an increasingly earlier stage - that leads to the ability to do less radical procedures."

She says fewer women are having mastectomies and that the smaller the tumour the less likely the disease has spread, thereby increasing breast cancer survival rates.

But he adds that this is difficult to reconcile with the results of the current 'post intervention' observation-based study, which suggests that screening does not have a direct impact.

Armstrong agrees with the paper's suggestion that improved treatments over the study period could be a key contributing factor to their findings, but says that it would have been "immensely valuable" to have had the 'interval cancer rate' for each country, which is a measure of how well the screening programs are performing.

"Just because something is implemented, does not mean it is done well," he says. "Frankly, I'd find it difficult based on the present evidence to go out there and say scrap screening programs."

Where does this leave us?

"I'm buggered if I know, but the good news is that breast cancer death rates are coming down."